Synergistic combination of gemcitabine and dietary molecule induces apoptosis in pancreatic cancer cells and down regulates PKM2 expression.

Ajay Pratap Singh,Archana Pandita,Samantha Vaishnavi,Siddharth Manvati,Shashank K Singh,Rameshwar N K Bamezai,Bhupender Kumar

doi:10.1371/journal.pone.0107154

Ajay Pratap Singh, Archana Pandita + Show 5 more

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https://doi.org/10.1371/journal.pone.0107154

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Abstract

Gemcitabine, an effective agent in treatment of cancer of pancreas, has undergone failures in many instances after multiple cycles of therapy due to emergence of drug resistance. Combination of dietary compounds with clinically validated drugs has emerged as an effective therapeutic approach to treat pancreatic tumors, refractory to gemcitabine therapy. In order to optimize a possible synergistic combination of Gemcitabine (GCB) with dietary molecules, Betuilnic acid (BA) and Thymoquinone (TQ), stand-alone IC50 dose of GCB, BA and TQ was calculated for pancreatic cancer cell lines. Fixed IC50 dose ratio of the dietary molecules in combination with reduced IC50 dose of GCB was tested on GCB resistant PANC-1 and sensitive MIA PaCa-2 cells for synergism, additive response and antagonism, using calcusyn. Combination index (CI) revealed that pre-treatment of BA and TQ along with GCB synergistically inhibited the cancer cell proliferation in in-vitro experiments. Pyruvate kinase (PK) M2 isoform, a promising target involved in cancer cell metabolism, showed down-regulation in presence of TQ or BA in combination with GCB. GCB with BA acted preferentially on tumor mitochondria and triggered mitochondrial permeability transition. Pre-exposure of the cell lines, MIA PaCa-2 and PANC-1, to TQ in combination with GCB induced apoptosis. Thus, the effectiveness of BA or TQ in combination with GCB to inhibit cell proliferation, induce apoptosis and down-regulate the expression of PKM2, reflects promise in pancreatic cancer treatment.

Highlights

Attempts have been madeto improve upon the efficacy of clinically validated drugs in combination regimen to enhance their response towards refractory tumors, including pancreatic cancer [1]
We investigated the effect of Betulinic acid (BA) or TQ with GCB, independently and in combination, on human adenocarcinoma cells, MIA PaCa-2 and PANC-1, to induce cell death
In vitrocombination studies of gemcitabine with betulinic acid and thymoquinone The chemo-sensitivity in pancreatic cancer cell lines, MIA PaCa-2 and PANC-1, towards the drug GCB and the dietary molecules, BA or TQ, was reflected in cell growth inhibition, calculated by IC50 (50% growth inhibition) at 48 hrs; and compared initially with the values obtained in a control cell line, FR2

Summary

Introduction

Attempts have been madeto improve upon the efficacy of clinically validated drugs in combination regimen to enhance their response towards refractory tumors, including pancreatic cancer [1]. A mechanistic link between diet and pancreatic cancer comes from its longrecognized interrelationship [4] One such dietary agent, which could be used in combination with GCB for treatment of pancreatic cancer, is Betulinic acid (BA), a naturally occurring penta-cyclic-triterpene with a variety of biological activities including potent antitumor properties [5]. Previous studies have shown the biological activity of thymoquinone (TQ) in pancreatic cancer cellsin vitro. This has revealed its chemo-sensitizing effect after the pre-exposure of cells to TQ (25 mmol/L) for 48 hrs, followed by gemcitabine or oxaliplatin, resulting in 60% to 80% growth inhibition as compared to 15% to 25% of inhibition with gemcitabine or oxaliplatinalone [17]

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